Annular combustion chamber for dissimilar fluids in swirling flow relationship

ABSTRACT

The characteristics of thermodynamically and aerodynamically dissimilar fluids in swirling flow relationship are established and/or varied to accelerate mixing and hence combustion in the combustion zone and mixing and hence cooling of the products of combustion, in the dilution zone of an annular burner.

United States Patent 91 Markowski ANNULAR COMBUSTION CHAMBER FOR DISSIMILAR FLUIDS IN SWIRLING FLOW RELATIONSHIP [75] Inventor: Stanley J. Markowski, East Hartford, Conn.

[73] Assignee: United Aircraft Corporation, East Hartford, Conn.

[22] Filed: Oct. 26, 1970 [21] App]. No.: 84,086

[56] References Cited UNITED STATES PATENTS 8/1949 Birmann 60/3965 2/1953 Williams..... 60/3965 10/1955 Schelp 60/3936 1 3,788,065 Jan. 29, 1974 2,773,350 12/1956 Barrett 60/3972 R 2,945,349 7/1960 Ritzi 60/3936 3,002,351 10/1961 S1oan..... 60/3982 P 3,030,773 4/1962 Johnson 60/3965 3,034,297 5/1962 Orchard 60/3965 3,078,672 2/1963 Meurer 60/3965 3,088,281 5/1963 S01tau 60/3965 3,373,562 3/1968 Wormser 60/3972 R 3,393,516 1 7/1968 Markowski .Q ..60/26l 3,479,823 11/1969 Parnell ..60/39.74 R

FOREIGN PATENTS OR APPLICATIONS 685,068 12/1952 Great Britain 60139.65 847,091 8/1952 Germany 60/3965 Primary Examiner-Doug1as Hart Attorney, Agent, or Firm-Vernon F. I-lauschild [5 7] ABSTRACT The characteristics of thermodynamically and aerodynamically dissimilar fluids in swirling flow relationship are established and/or varied to accelerate mixing and hence combustion in the combustion zone and mixing and hence cooling of the products of combustion, in

the dilution zone of an annular burner.

74 Claims, 49 Drawing Figures PATENTEUJAH 2 9 I974 SHEET 01 0F 0 2 0 Gm ll 1 1 W 5m 57 r5 5 5 x F wy W 4 I v2 1.5 2/ War I at W w. Mim c f; )w 5 7% w. I. M2. m 6 Z I MZMC F Wuw w//M\WVX FIC3-4 PATENTEUJAN 29 I974 SHEEI 06 [IF SHEET 07 0F w Z W w w lw i D: 7N

5. 3 1 27 a a F PATENTEDJM29 m4 3,788,065

SHEEI 080F 11 PATENTEDJAHEQ 1974 SHEEI 09 0F FIG-33 FlG 29 ,5 5 7&4 F 132 FIG.35

FIG-37 FIG-34 Pmgmmmzsmm 3,788,065

SHEET 100? 11 FIGQBS 'IIIIJIIIIIIIIIIII/IIIIJK FIG-43 FIG.44

ANNULAR COMBUSTION CHAMBER FOR DISSIMILAR FLUIDS IN SWIRLING FLOW RELATIONSHIP CROSS-REFERENCES TO RELATED APPLICATIONS This application contains subject matter related to the following two applications assigned to the same assignee:

l. Application, Ser. No. 84,087, filed concurrently herewith for Shortened Afterburner Construction for Turbine Engine" and 2. Application, Ser. No. 84,088, filed concurrently herewith for Combustion Chamber Having Swirling Flow.

BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to the controlled mixing of two thermodynamically and aerodynamically dissimilar fluids and particularly to the use of swirling flow between two dissimilar fluids in annular combustion chambers, such as the burners and afterburners of turbine engines, to accelerate both the combustion process and the temperature reduction process of the products of combustion in the dilution zone of the burner.

2. Description of the Prior Art In the combustion chamber and burner art, it has been conventional to burn in a cylindrical chamber by discharging an atomized fuel spray into the center thereof with air being discharged therearound through a vaned cascade at tangential velocity V, so as to form a recirculation zone of the atomized fuel and swirling air so mixing. This recirculation zone is formed because the angular momentum of the air is proportional to the tangential velocity V, thereof times the radius of the air particle involved from the burner central'axis, accordingly, any air which is at or near the burner axis is of minimal or zero radius so that the tangential velocity attempts to go to infinity with the result that nonswirling secondary air is brought in around the recirculation zone for mixing with the stagnated fuel-air mixture downstream ofthe recirculation zone and for cooling the walls of the combustion chamber, as typically shown in U.S. Pat. No. 3,498,055.

These prior art burners are called can burners, because of their cylindrical shape, or can-annular burners, because they have a series of can-shaped inlet sections opening into an annular main section. The momentum-velocity system of establishing a recirculation zone is used in the can portion of both.

The momentum-velocity system of establishing a recirculation zone does not work in an annular combustion chamber because all combustion stations are of substantial radius and therefore I utilize the interdigitation of the swirling sheets of dissimilar fluids to perform this function.

The U.S. Pats. to Johnson No. 3,030,773 and Sanborn No. 2,473,347 utilize swirling flow in combustion chambers but it will be noted that these are cylindrical or can-type combustion chambers and that none of this prior art teaches the use of establishing an unstable interface between two swirling dissimilar fluids for the purpose of accelerating mixing and combustion therebetween by establishing and/or control of the fluid density and tangential velocity V, to produce dissimilar conventional can or cylindrical burner is shown in afterburner form in U.S. Pat. No. 2,934,894.

Other than the aforementioned type of swirling flow to assist in establishing a recirculation zone in a cylindrical or can burner or in an annular burner having a plurality of substantially cylindrical, circumferentially extending can burner spray nozzles positioned circumferentially thereabout as in U.S. Pat. No. 3,000,183, swirling flow is generally discouraged in conventional combustion chambers and straightening vanes are provided for this purpose.

Swirling flow has been suggested for combustion chambers in certain patents, however, including Ferri et al U.S. Pat. No. 2,755,623 which teaches the concept of causing the fuel-air mixture passing through a combustion chamber to flow in swirling motion so as to improve combustion, however, it should be noted that in theFerri et al. patent there is but a single swirling stream and he therefore does not achieve the mixing and accelerated combustion advantages of my invention. The U.S. Pat. to Meurer No. 3,078,672 causes swirling air to be passed through a can-type burner and causes a solid sheet or film of fuel to be passed along the inner surface of the burner outer wall to be vaporized and to burn with the swirling air at the outer wall. Combustion takes place at the interface between the air and the fuel at the outer wall of the combustion chamber and the products of combustion move inwardly to be gathered and recycled through duct 22. Meurer clearly does not teach the concept of mixing and combusting two dissimilar fluids by control of the parameter products taught herein. My U.S. Pat. No. 3,393,516 illustrates curved flow in an exhaust gas deflector of a turbo-fan engine but it should be noted that there is no mixing and combustion in connection with the curved flow, in fact, such would be undesirable.

SUMMARY OF THE INVENTION -mixing limited. The time of burner length required to obtain complete combustion can be limited by that necessary to mix together the hot gases and the cool fuel-air mixture. Accelerated mixing in both the combustion and dilution zones will shorten the length of the combustion chamber and hence shorten the length and weight of the engine.

A primary object of the present invention is to provide an improved annular combustion chamber by establishing, controlling and/or varying the product parameter pVF, where p is fluid density and V, is fluid tangential velocity, between two dissimilar swirling fluids to establish an unstable interface therebetween to accelerate mixing and hence combustion in the combustion zone and mixing and hence coolingin the dilution zone of the combustion chamber.

In accordance with the present invention, this product parameter is established, controlled and/or varied so that the product parameter of the fluid which is flowing at the lesser radius about the combustion chamber axis is greater than the product parameter of the fluid which is flowing at the greater radius, so that the mixing ratio in the combustion chamber is determined by the ratio pV, (inner flow) pV, (outer flow).

In accordance with a further aspect of the present invention, the interface between two dissimilar swirling combustion chamber fluids are established or controlled so that outside-inside burning occurs in the combustion chamber.

The invention permits accelerated mixing and combustion or accelerated mixing and dilution to occur in several annular combustion chamber configurations, for example, in the concentric flow mixer configuration, the barberpole mixer configuration, and the bent tube or folded combustion chamber mixer configuration.

In accordance with a further aspect of the present invention, a combustion chamber can be fabricated so as to consist of a combustion zone and a dilution zone with either or both of these zones utilizing a concentric mixer, a barberpole mixer, or a bent tube mixer and any of these mixers can be used with a conventional combustion zone or dilution zone.

It is a further aspect of the present invention that utilizing any of these mixing constructions, combustion can take place utilizing either the premixed or diffusion principle.

It accordance with a further aspect of this invention, hardware is provided to establish, control or vary the orientation of two concentric fluid streams of different thermodynamic and aerodynamic states in such a way that the product parameter density, p, of the inner stream times the tangential velocity V, of the inner stream is greater than the corresponding product parameter of the outer stream.

In accordance with still a further feature of the present invention, compound mixing in radial, parallel staging occurs both in the combustion zone and the dilution zone of an annular combustion chamber in which the combustion zone and the dilution zone are axially staged in series so as to reduce the overall length of the combustion chamber and hence the engine length and weight.

In accordance with still a further feature of this invention, several modifications of the pilot combustion zone in a concentric mixer for a primary combustion zone are usable and of advantage depending upon the particular requirements of the combustion chamber configuration involved.

In accordance with still a further aspect of the present invention. triggers are used to disturb the unstable interface between two swirling streams to accelerate mixing and either combustion or cooling therebetween.

In accordance with still a further aspect of this invention, a combination flameholder and/or trigger can be used in a swirling flow annular combustion chamber to accelerate mixing and burning of the products of combustion from the recirculation zone established downstream of the flameholder and the fuel-air mixture passing around the flameholder.

In accordance with still a further feature of this invention, swirling fluid interface trigger mechanisms are provided in the form ofa corrugated and tapered rings,

which may have holes or scoops therein for noise deadening and trigger mechanism cooling purposes.

In accordance with still a further feature of this invention, combustion apparatus is' provided in which combustion or dilution zones are located in series in which mixing occurs in both zones at parallel radial stations.

In accordance with a further teaching of this invention, the unstable interface between two swirling streams of fluid which are established by the product parameter criterion taught herein can be physically interrupted or disturbed by a variety of trigger mechanisms.

It is a further teaching of this application to establish a stable interface criteria between the cooling air for a combustion chamber liner and the products of combustion.

In accordance with still a further feature of my invention, swirling flow in an annular combustion chamber invites the use of flameholders therein and the use of a substantial variety of fuel injecting devices to be used therewith.

Other objects and advantages of the present invention may be seen by referring to the following description and claims, read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of two dissimilar fluids flowing in swirling relationship in separated coannular passages and then joining and mixing in a single annular passage.

FIG. 2 is a schematic showing in cross-section of the FIG. 1 flow representation.

FIG. 3 is a vector diagram of the fluid flowing in swirling fashion in the FIG. 1 and 2 environment and the other environments disclosed herein.

FIG. 4 is a showing of the static pressure distribution across the outer and inner swirling fluid flows of the FIG. 1 and 2 environment.

FIG. 5 is a schematic representation of mixing occuring in two fluid streams flowing in side-by-side relationship and which are caused to swirl in passing through a bent tube.

FIG. 6 is a schematic cross-sectional showing of a barberpole swirl mixer.

FIG. 7 is an end view taken along line 7-7 of FIG. 6.

FIG. 8 is a showing of an annular combustion chamber concentric mixer utilizing the premixed burning principle.

FIG. 9 is similar to FIG. 8 but utilizing the diffusion burning principle.

FIG. 10 is a cross-sectional showing of an annular combustion chamber barberpole mixer used in the combustion zone and utilizing the premixed burning principle.

FIG. 11 is similar to FIG. 10 but utilizing the diffusion burning principle.

FIG. 12 is a showing of a premixed combustor employing bent tube mixing in a folded combustion chamber which is preferably of the annular type.

FIG. 13 is a showing of a modern turbine engine of the type used in the modern aircraft and shown utilizing my invention.

FIG. 14 is a cross-sectional showing of an annular combustion chamber using a concentric mixer in both the combustion zone and the dilution zones.

FIG. 15 is a showing ofa vane of an annular vane cascade and its actuating mechanism to make the cascade variable angle so as to vary the angle at which the gases passing therethrough are discharged.

FIG. 16 is a cross-sectional showing of an annular combustion chamber using a barberpole mixer in both the combustion zone and dilution zones thereof.

FIG. 17 is taken along line 17l7 of FIG. 16.

FIG. 18 is an enlarged, unrolled showing of the combustion chamber outer liner of FIG. 16 to illustrate the orientation of the outer liner helical slots in the barberpole mixer of the dilution zone.

FIG. 19 is a cross-sectional showing of the vaned, helical slots use in the inner Wall of the dilution zone mixer of FIG. 16 and is taken along line l919 of FIG. 16.

FIG. 20 is a modification of the helical slots shown in FIG. 18 and can be used in the barberpole mixer either in the combustion zone or the dilution zone of an annular combustion chamber.

FIG. 21 is a cross-sectional showing of an annular combustion chamber having axially staged combustion and dilution zones and utilizing a concentric mixer in the combustion zone and a barberpole mixer in the dilution zone.

FIG. 22 is a cross-sectional showing of an annular combustion chamber having a conventional combustion zone and dilution zone of the folder burner or bent tube variety utilizing my invention.

FIG. 23 is a modification of the primary combustor portion of the combustion zone mixer shown in FIG. 14.

FIG. 24 is a modification of the concentric mixer used in the combustion zone of an annular combustion chamber which may be substituted for the type shown in FIG. 14.

FIG. 25 is an enlarged, partial, cross-sectional showing of the flameholder member taken along line 25-25 of FIG. 24.

FIG. 26 is a showing ofa modification of the combustor shown in FIG. 25.

FIG. 27 is an enlarged showing of the FIG. 26 construction taken along line 27 of FIG. 26.

FIG. 28 corresponds to FIG. 27 and shows the secondary flow patterns between the helical guide vanes.

FIG. 29 is still another modification for the primary combustion chamber shown in FIG. 14.

FIG. 30 is a schematic representation of two swirling fluids flowing through annular passages with a splitter duct therebetween and with a trigger mechanism attached to the downstream end of the splitter duct.

FIG. 31 is an end view of the FIG. 30 construction.

FIG. 32 is a cross-sectional showing of a trigger mechanism which may be substituted for the trigger mechanism shown in the splitter duct of FIG. 14.

FIG. 33 is a showing ofthe trigger mechanism of FIG. 32 shown with the splitter duct unrolled for purposes of better illustration.

FIG. 34 shows another modification of trigger mechanism of FIG. 14.

FIG. 35 is a showing of a further trigger mechanism modification utilizing plural rows or patterns of helical slots in or near the trailing edge of a splitter duct.

FIGS. 36 and 37 are plan and end views of still another trigger mechanism modification of the variety which utilizes both a helically slotted and helically corrugated downstream end on a splitter duct to perform their swirling fluid interface triggering function's.

FIG. 38 is a showing of still another trigger mechanism modification utilizing a combination of helical slots and scooped projections cooperating therewith at the downstream end of a splitter duct to accelerate mixing.

FIG. 39 is a representation of irregular trigger corrugation utilized for the purpose of noise suppression.

FIGS. 40 and 41 depict annular combustion chamber flow passage modifications which can be used because of the swirling flow therethrough to retard or prevent flow separation of the boundary layers along the diffuser walls.

FIGS. 42a and 4212 are showings of an annular combustion chamber utilizing swirl flow and further utilizing a compound vane cascade at the inlet thereof to control the amount of swirling at the various radial stations across the cascade so as to discourage boundary layer flow separation and permit the utilization of shortened diffuser section in the combustion chamber, thereby reducing the length of the combustion chamber.

FIGS. 43 and 44 are showings of the axial velocity profile and tangential velocity profile of the air immediately downstream of the cascade of compound vanes of FIG. 42.

FIG. 45 is a cross-sectional showing of a scoopedaperture which may be used with trigger mechanisms, such as those shown in FIG. 14.

FIGS. 46 thru 48 are showings of annular combustion chambers utilizing radially staged combustion for reduced combustion chamber and engine length and having provisions for engine power performance control.

DESCRITPION OF THE PREFERRED EMBODIMENT To fully explain the subject matter of this application, it is deemed desirable to first describe the theory involved.

My observation of the dynamic behavior of concentric dissimilar swirling flows leads to the discovery of a fluid interface instability phenomenon that can be used to increase the mixing rate between the dissimilar fluids and which therefore is of particular interest in combustion chambers to accelerate combustion by increasing the mixing rate and hence the effective flame speed and also to accelerate the mixing which takes place in the combustor dilution zone wherein the products of combustion are cooled by mixing with cooling air before being passed through the turbine. As used herein the term dissimilar fluids means fluids which are thermodynamically and aerodynamically dissimilar. This phenomenon of interest and its characteristics will now be described by referring to FIGS. 1 and 2. In these figures, two dissimilar fluids are flowing in concentric swirling flow patterns and are isolated initially by a cylindrical separator wall 10, which is positioned between cylindrical ducts l2 and 14 so that walls 10, 12 and 14 are concentric about centerline or axis 16 and cooperate to define concentric annular passages 18 and 20. While the outer fluid will be described as the hot fluid and the inner fluid the cold fluid, this does not have to be the case. As the swirling fluids pass downstream of the separator termination point 22, interface 24 is established therebetween. As best shown in FIG. 3, the velocity of each fluid may be represented by the flow vector diagram shown where V, is axial velocity, V, is tangential velocity and V is actual velocity in the indicated direction. Fluid flowing in such a manner comes under the primary influence of two forces of significant magnitude, namely, centrifugal forces and forces due to the pressure gradient which exists in the duct through which the fluid is flowing. At a given radius, the centrifugal force, F is proportional to the mass of the fluid, and consequently the density, p, of the fluid, and the square of the tangential velocity or tangential velocity component V,, of the fluid. The pressure gradient force, F,,, is proportional to the radial pressure gradient and results from the radial difference in static pressure across the radially projected area of the fluid element. During the passage of the two fluids through annular passages and 18, these forces are in equilibrium, as best shown in FIG. 1 with respect to simulated fluid particles 26 and 28, and the fluid flows in its helical path.

Downstream of separator 10, where both fluids enter common annular passage 30, the two fluids are in direct contact with each other and therefore are capable of influencing one another.

By viewing FIGS. 1 and 4 it should be noted that the static pressure distribution profile 32 for the outer swirling, usually hot fluid is considerably less steep than the static pressure distribution profile 34 of the inner swirling cold fluid, and this is reflected in the magnitude of the pressure gradient force, F,,, indicated to be acting upon the outer stream element 28 and the inner stream element 26 in FIG. 1. These pressure gradient forces acting on elements 28 and 26 are balanced by the centrifugal force, F action thereon because of the radial equilibrium of each individual stream.

My study and observations have lead me to the discovery that interface 24 between these two dissimilar fluids is unstable ifthe product parameter pVf", i.e., the product of the fluid density p and the square of the tangential velocity V, of the fluid, of the outer radial fluid is less than that of inner radial fluid. This instability is demonstrated by introducing a disturbance into the interface 24 such that a local interface convolution 36 projects radially outwardly into the outer radius fluid region. The element of fluid 26 in this projection 36 is exposed to the relatively small radial pressure gradient, F n. o the outer radius fluid region but still retains its high centrifugal force. F This establishes an unbalance of forces on element 26' and results in an acceleration of the disturbance radially outward to cause the convolution size and penetration into the outer radius fluid to increase, thereby increasing the rate of mixing between the two fluids. In similar fashion, a convolution 38 of the interface 24 projecting radially inward will result in a force unbalance on fluid element 28' which remains under the relatively small centrifugal force, F and comes under the influence of the substantially larger pressure gradient force, F and is consequently accelerated radially inward to result in rapid inward growth of convolution 38 and accelerated mixing between the two streams.

The relative magnitude of the unbalanced forces just described may be assessed by considering the outer fluid as a combusted gas from a combustion chamber which typically would lower the density by a factor of perhaps four relative to the unvitiated innerstream. Since the tangential velocity of the gas in a typical combustor pilot will change relatively to a smaller magnitude, the unbalanced force is seen to be three-quarters or more of the maximum centrifugal force on the two fluids. This magnitude of the unbalanced force is decidedly first order and represents a large acceleration potential available to expedite the radial movement of the two concentric fluids into a helical sheet mode of flow.

My invention is the utilization of this phenomenon in accelerating mixing between two dissimilar swirling fluids in annular combustion chambers of the type used in turbine engines to both accelerate combustion and accelerate the dilution ofthe hot products of combustion with cooling air before passage through the turbine.

While I have described this mixing phenomenon in FIGS. 1 and 2 in the context of coannular, dissimilar, swirling streams, it should be borne in mind that the same mixing acceleration can be achieved in other environments such as the bent tube environment shown in FIG. 5 wherein both dissimilar streams flow through duct 66 which includes a straight portion 68 and bent portion 70, which has center of curvature 79, and which has splitter or separation member 72 at its upstream end cooperating with duct 66 to define two passages 74 and 76 through which the two dissimilar streams flow with the fluid in the outer passage 74 having lower pV, than the fluid in the inner passage 76 so that when the two fluids join in passage 78 they establish the unstable interface and accelerate mixing described in connection with FIGS. 1 and 2 as they become concentric swirling streams upon entering bent tube section 70, in view of the fact that the product parameter relationship p,, V,,, p, V where p,, and p,. are the density of the hot outer, swirling stream and the cold, inner, swirling stream respectively, and V,,, and V, are their respective tangential velocities, which are actually their through-flow velocities in the bent tube construction.

This accelerated mixing can also be established by use of the barberpole swirl mixer 80 shown in FIGS. 6 and 7. The term barberpole is selected to describe this mixer because it causes the two dissimilar fluids to form into a series of interdigitated, swirling sheets or fingers. This mixer consists of outer wall 82 and inner wall 84 which preferably diverge to form diverging passage 86 through which the swirling main fluids flow and which have selectively oriented helical slots 88 and 90 extending therethrough, respectively, through which the secondary fluids flow and are caused to enter parallel to the main stream flow. As best shown in FIG. 7 the direction of helical slots 88 and 90 are such that they are locally parallel to the direction of the swirling main flow. By use of appropriate guide vanes and inlet conditions for the secondary flows the product parameter flow criterion: pV, inner secondary pV, main flow and pV, outer secondary pV, main flow are attained. With this flow criteria the sheets of secondary flow will penetrate rapidly across the main flow because the same mixing phenomenon previously described in connection with the FIGS. 1 and 2 construction occurs here between each swirling fluid sheet and the two swirling sheets of dissimilar fluids adjacent thereto. Accordingly, total required mixing will occur more rapidly. In certain situations, it may be desirable to use a barberpole mixer of the type shown in FIGS. 6 and 7 in which the helical slots are used in one of the walls, 82, or 84 only. In the FIGS. 6 and 7 barberpole construction, the main flow is preferably hot air and the secondary flows are cooler air and the slots 88 and 90 are oriented to bring about not only helical flow but helical flow substantially parallel to the main flow direction.

Any of these mixers, that is, the concentric mixer, barberpole mixer and the bent tube mixer can be effectively utilized in the combustion zone of a combustor or burner to increase the rate of mixing and hence rate of combustion and effective flame speed so as to reduce overall burner length as illustrated in FIGS. 8-12. To emphasize similarity of function the reference numerals of FIGS. 1, 2, 6 and 7 will be repeated in describing the FIGS. 8-12 constructions.

In practice when using these mixers in the combustion zone of a combustor, one of the swirling streams is used as a hot pilot to initiate combustion in the other swirling stream, which is a fuel-air mixture. Burning occurs when the two streams mix.

We will now consider which stream to select as the pilot stream.

In the caseof the concentric mixers and combustion chambers shown in FIGS. 8 and 9 and the bent tube combustion chamber shown in FIG. 12, it is apparent that the pilot stream should be the outer stream because the density depression caused by heating helps in achieving the desired interfaced instability criteria pV, inner pV, outer. In the barberpole mixers and combustors shown in FIGS. 10 and 11, the choice of which stream will act as the heated pilot is not as obvious. In view of the density depression associated with fluid heating, it is apparent that the pilot stream should be one of the streams requiring a low pV, product parameter and hence the pilot stream should not be the secondary flow in inner passage 114. The main stream 112 should be chosen as the pilot stream to avoid the severe wall cooling problems which would be caused by injecting a hot gas secondary stream from passage 112 along outer walls 82. In view of the low density of the pilot stream, the product parameter pV, for the outer secondary fluid can be made smaller than the product parameter pV, of the pilot to obtain the desired rapid mixing by permitting little or no tangential velocity V, as it passes through slots 88. The desired interface instability criteria between the pilot flow from passage 112 and inner secondary flow from the passage 114 is satisfied by the use of the required turning vanes or the like to adjust the tangential velocity (V,) level to satisfy the required criteria pV, inner pV, pilot. Of course, the combustion process in the pilot decreases the density of this stream thereby assisting in satisfying this criteria.

FIG. 8 depicts a concentric mixer in a combustion chamber combustion zone where concentric passages 18 and are formed between concentric ducts 12, 10 and 14 and wherein splitter duct 10 terminates short of the outer ducts so that the outer ducts form combustion zone 30 downstream thereof. Appropriately positioned inlet guide vanes or other mechanisms cause swirling fluid to pass through each of passages 18 and 20. The flow in passage 20 serves as the pilot combustion stream in that pilot fuel is injected thereinto through pilot fuel nozzle mechanism 92 which sprays atomized fuel into the fluid passing therethrough just upstream of flameholder 94 to form pilot combustion zone 96 downstream thereof wherein the fuel-air mixture is burned and vitiated after appropriate ignition in combustion zone 96 so that the swirling fluid discharging from passage 20 becomes a pilot to ignite and sustain combustion in the swirling fluid passing through passage 18. This fluid in passage 18 has fuel added thereto by secondary fuel injector 98 to form a fuel-air mixture of the characteristics that the product of its density and tangential velocity squared pV, is greater than the corresponding product parameter for the outer swirling pilot stream of passage 20 so that accelerated mixing and subsequent combustion takes place between the two fluids in combustion zone 30. The burner shown in FIG. 8 utilizes the premixed burning principle in that fuel is sprayed into the secondary stream 18 prior to entering the mixing and combustion zone 30 and this stream becomes a combustible fuel-air mixture that is subsequently ignited and vitiated when it is mixed with the hot pilot gases or flame from stream 20.

Such a concentric mixer used as a combustor utilizing the diffusion burning principle is shown in FIG. 9. The diffusion burning technique works on a different principle than the premixed burning technique. In the diffusion burning technique, the pilot fuel from nozzle 92 is fully combusted and fully vitiated in pilot combustion zone 96 such that little or no oxygen remains therein and, accordingly, any fuel added thereto downstream of fully vitiated interface 100 can be vaporized only by the hot products of combustion from pilot zone 96. This phenomenon is taken advantage of in the diffusion burning principle and secondary fuel is discharged into stream 20 by secondary fuel nozzles 101 but this secondary fuel cannot burn until it is mixed with the secondary air being passed in swirl fashion through in stream 18. In this case it will be seen that no fuel whatsoever is directed into stream 18 and that the pilot stream 20 carries not only the heat necessary to initiate combustion and mixing in mixing and combustion zone 20 but also carries the fuel to support this combustion process, when mixed with the air from passage 18.

FlGS. l0 and 11 depict barberpole mixers of the type shown in FIGS. 6 and 7 utilized to form combustion chambers of the premixed burning and diffusion burning variety. In the FIG. 10 construction, ducts 102, 104, 106 and 108 are positioned concentrically about centerline 16 to form coannular passages 110, l 12 and 114 therebetween. Guide vanes or the like are used to produce swirling flow in passages 110, 112, and 114 to achieve the desired tangential velocity V, or, as in all other configurations disclosed, this flow may be accepted directly from a compressor which does not have straightening vanes at its outlet. Ducts 104 and 106 join walls 82 and 84 which define passage 86, which is preferably divergent and is the main combustion zone 60. Fuel is sprayed through pilot nozzles 92 into annular passage 112 to be combusted in pilot combustion zone 96 downstream of flameholder 94 to serve as the pilot stream. Secondary fuel is injected into passages and 114 through secondary fuel nozzles 98 in atomized form to be mixed with the air passing therethrough and to pass therefrom through opposed helical slots 88 and 90, respectively, to be discharged as a fuel-air mixture flow substantially parallel to the swirling pilot stream being directed from pilot combustion chamber 96 for accelerated mixing and subsequent combustion with the pilot stream in mixing and combustion zone 60. As in the case of the barberpole" mixer, the direction of flow of the secondary fuel-air mixture through slots 88 and 90 are adjusted by suitable guide vanes to satisfy the instability criteria pV, outer secondary pV, pilot and pVf" inner secondary pV, pilot.

In the FIGS. -11 construction, all air entering passage 96 enters with a selectively established tangential velocity V,. This spinning of the air will lower the static pressure in the pilot combustion chamber 96. The premixed fuel-air mixture passing at a larger radius through passage 110 does not necessarily have swirl added thereto. In passage 110 air enters the combustion zone 60 through slots or helical hole pattern 88 in wall 82, such holes 88 are helical in nature or holes or slots designed in helical pattern. This air will accelerate radially through the holes 88 due to the static pressure drop across the holes or slots and once inside primary or pilot combustion zone 60, this air will continue to be accelerated radially inward because of the radial pressure gradient established by the swirling pilot fluid from passage 96 in combustion chamber 86. By admitting this fuel-air mixture through helical slots or holes or slots in a helical pattern, 88, a very rapid combustion pattern of helical layers will be established in the main combustion zone 60. The fuel-air mixture layers thus formed are burned as interdigitated mixing with the swirling air from the pilot proceeds. As the fuel-air mixture through slot 88 is burned, its radial inward motion is locally further accelerated because the consequent decrease in the density lowers its pV, product parameter even further and the radial pressure gradient will accelerate a small portion of burned gas faster than unburned gas. The portion of the fuel-air mixture which passed through helical slots or hole patten 90 has a tangential velocity V, imparted thereto that is sufficiently high for pV, p\ of the vitiated pilot gases. Therefore the admitted fuel-air mixture will form helical sheets which will interdigitate with the hot spinning air entering zone 60 from the pilot region 96 and be accelerated radially outward. While the density, p, of the locally burned surface layer of the swirling fuel-air mixture streams will decrease substantially during burning, it will retain the same tangential velocity, V,, since its angular momentum is unaffected by the change of thermodynamic state. Consequently, the local pV, product parameter of the sheets entering through the slots 90 will be substantially reduced and its acceleration due to the radial pressure gradient will also be reduced as the sheet burns. However, the unburned portion of the helical layer will continue to be accelerated radially outward, thus continuing to stir the flame front until it is completely burned.

Viewing FIG. 11 we see the barberpole mixer used as a combustion chamber utilizing diffusion burning in which concentric, preferably cylindrical ducts 102, 104, 106 and 108 are positioned concentrically about centerline or axis 16 to form coannular passages 110, 112, and 114 therebetween, with ducts 104, 106 extending into preferably divergent walls 82 and 84 to form section 86 which defines the main combustion zone 60. Pilot fuel from nozzles 92 is admitted in atomized form to passage 112 upstream flameholder 94 to be fully combusted and vitiated in pilot combustion chamber 96 so that the products of combustion are fully vitiated upstream at interface 100. Secondary fuel is admitted to annular passage 112 downstream of interface 100 through secondary fuel nozzle 101 to be heated and carried with swirling combustion products of the pilot combustion chamber 96 into combustion zone 60, secondary air is passed through annular ducts 110 and 114 and through opposed helical slots 88 and 90, respectively, into mixing and combustion chamber 60 to be mixed with, the hot, fuel rich, flow from pilot stream duct 112. As the mixing process proceeds the excess fuel in the pilot stream comes into contact with the sheets of secondary air entering through slots 88 and and combustion occurs at the multiplicity of interface between these flows.

FIG. 12 depicts a bent tube mixer in the form of a folded burner or combustor of the premixed burning variety. In the FIG. 12 premixed burning configuration, the first fluid is passed through passage 74 to have atomized fuel added thereto from pilot fuel nozzle 92 and so that a pilot combustion zone is established at 96 so as to provide an outer pilot stream entering the curved section 70 of curved duct 66 to serve as a pilot to institute mixing with and subsequent combustion of the fuel-air mixture being introduced through passage 76 into mixing and combustion chamber 30. The fuel-air mixture in passage 76 is generated by the passage of fluid therethrough and the introduction of atomized fuel thereinto through secondary fuel spray nozzles 98. It will accordingly be seen in the FIG. 12 construction that a hot pilot stream is established as the outer swirling stream with respect to the inner colder fuel-air mixture stream, both of which are concentric about center of curvature 79 to cause accelerated mixing and combustion therein in view of the flow criteria pV, inner pV, outer. It will be evident to those skilled in the art that the construction shown in FIG. 12 could be made of the diffusion variety by moving pilot fuel nozzle 92 and flameholders 94 farther upstream so that combustion in the pilot combustion zone 96 is completed and a fully vitiated interface corresponding to 100 of FIG. 9 is established sufficiently far upstream of the termination of splitter member 72 that secondary fuel can be injected into passage 74 upstream of the termination of splitter member 72 to be introduced into combustion chamber 30 in uncombusted form for mixing and combusting with secondary air which would flow through passage 76.

To assist in accelerating mixing between the two swirling flows in the concentric and bent tube mixers, it is sometimes desirable to use trigger mechanisms at the end of ducts which serve as splitter ducts between the swirling flow of two different fluids, such as triggers 164 and 166 shown in FIG. 14, to physically disturb the interface between the swirling fluids. A discussion of the theory of operation of these trigger mechanisms is believed to be helpful at this point and reference is first made to FIGS. 30 and 31 in this regard. In FIG. 30 we see trigger mechanism 166 positioned at the downstream end of splitter duct 246 which is of circular cross-section and positioned concentrically about axis 16 and cooperates with outer cylindrical duct 248 and inner cylindrical duct 250 to define outer annular gas passage 252 and inner annular gas passage 254. For purposes of illustration, it should be considered that a hot fluid, which is to be the pilot fluid, is passed through passage 252. This hot outer fluid has a density p,, and a tangential velocity V,,,. A second fluid, which is preferably a cold (high density) combustible mixture, is passed through inner annular passage 254 and has a density of p and a tangential velocity V To effect accelerated mixing between these two fluids of passage 252 and 256, it is essential that the mixing criteria p V,,, p, V exists to establish an unstable interface between two swirling fluids. Above and beyond this, the use of trigger 166, which is shown to be a convoluted sheet metal ring member attached to the downstream end of splitter duct 246 further serves to accelerate mixing and combustion. Trigger 166 defines convolutions which follow helical paths growing in amplitude in a downstream direction and as the fluids of passage 252 and 254 pass thereover, a regular pattern of radial fluid motion will be initiated outwardly and inwardly due to the change of flow direction imparted to the fluids by trigger mechanism 166. The motion thus initiated will grow because of the instability of the interface. Such a trigger mixer has been successfully demonstrated using air at 200 Fahrenheit and 800 Fahrenheit as working media.

The amount of tangential mixing induced by fluid shearing at the helical sheet interface will depend upon the difference between the circulation per radian of the fluids in ducts 252 and 254.

The use of trigger mechanisms provides the advantage of controlling the location, size and shape of the disturbance at the interface between the two fluids and it will be appreciated that in constructions where trigger mechanisms are not used the disturbance of the interface is caused by turbulence only and is therefore random in nature.

Of particular interest is a piloted combustion application of such a triggered inside-out mixing configuration as shown in FIGS. 30 and 31. Here, the hot vitiated pilot flow would be the outer radius fluid having a low pV, product parameter, while the cold combustible mixture would be the inner radius fluid having a high pV, product parameter. FIG. 31 is a showing of the combustion-pilot primary combustion zone downstream of trigger [66. The flame front where active combustion occurs is located at the interface 255 and 253, respectively, of the triggered helical sheets of hot pilot flow from duct 252 and cold combustible mixture flow from duct 254. As shown in FIG. 31, the flame speed, F/S, moves against the trigger helical current of the combustible mixture flowing radially outward and into the hot mass of pilot flow. As the combustion occurs at the flame front, elements of air undergo an abrupt density change in a high centrifugal field with resultant release of the acceleration potential to magnify the local turbulence and effective flame speed. This local stirring action, i.e., increased turbulence, is superimposed upon the interface of the triggered mixing of the initial hot pilot and cold combustible mixture flows. The triggered hot pilot gas from passage 252, which comprises a radially inward directed current, has an interface flame speed that moves with the current, as well as laterally into the unburned mixture. Again, the local magnitude of turbulence is increased at the flame front by the abrupt fluid density changes in a strong centrifugal field which increases the effective flame speed. The difference in circulation per radian for the initial hot pilot flow and cold combustible mixture provides a superimposed tangential mixing through tangential shearing action.

Another trigger mechanism, which could be used as a substitute for trigger 166 in the FIGS. 14 and 30 construction, is shown in FIGS. 32 and 33. As shown in FIG. 32, splitter duct 246 and ducts 248 and 250 are used in the same fashion as in the FIG. 30 construction. Hot products of combustion flow between ducts 246 and 248, while the cooler fluid, such as a fuel-air mixture, flows in the passage between ducts 246 and 250. Trigger mechanism 258 is located at the downstream end of splitter duct 140 and consists of a series of oppositely oriented vane 260 and 262 pairs forming vortex generators which are spaced circumferentially about splitter duct and extending radially outwardly from the splitter duct and in any desired number of axially spaced rows. Once again, it is the object of trigger mechanism 258 to convolute the interface between the hot products of combustion flowing on one side of splitter duct and the cooling air or fuel-air mixture flowing in passage on the other side of the splitter duct so as to take advantage of the mixing criteria in that the pV, product parameter of the hot gases flowing at the greater radius is less than the pV, product parameter of the cold air or fuel-air mixture flowing at a lesser radian at the interface therebetween and any convolution will react with the respective pressure gradients in the hot and cold regions to cause radial mixing currents with cold air currents moving into the hot flow in helical sheets and the hot fluid currents moving into the cold region in helical sheets. The flow at the interface downstream of the trigger plane is unstable and the trigger configuration establishes the helical sheet mixing patterns. This mixing occurs from the inside (minimum radial station) to the outside (maximum radial station) and shortens the length of the combustion chamber and engine by accelerating the mixing process.

Referring to FIG. 34 we see still another modification of a splitter duct trigger which could be used in place of trigger 166 of FIG. 14. The trigger of FIG. 34 consists of a series of helically oriented and circumferentially positioned slots 260 at the downstream end of splitter duct 140. The slots are preferably oriented to be parallel to the direction of flow, V, of either the hot or cold gas streams and serves to trigger or disturb the unstable interface which exists between the swirling hot gas flow from the combustion chamber flowing outside splitter duct and the swirling colder air of the cooling gas stream flowing inside of the splitter duct 140 so as to accelerate intermixing.

An additional trigger embodiment is shown in FIG. 35 wherein a plurality of helically extending and circumferentially positioned slots 262 are positioned forward or upstream of slots 260 of the type shown in FIG. 34. Thereby adding to the mixing advantage of the trigger device by utilizing plural slot rows arid/or patterns.

Still a further trigger configuration is shown in FIGS. 36 and 37 wherein slots comparable to slot 260 of FIG. 34 are fabricated so as to be elongated and are circumferentially positioned helical slots 264. In this configuration, the after end of splitter duct 140 is fabricated, as shown in FIG. 37, to be corrugated in shape so that the FIGS. 36 and 37 trigger is a combination of the slotted trigger of FIG. 34 and the convoluted trigger of FIG. 30.

Still another form of trigger is shown in FIG. 38 wherein scoops 266 are added to helical slots 268, which are comparable to slots 260 of FIGS. 34 and 35 and which serve to scoop the cold spinning air from a construction comparable to the FIG. 14 construction flowing on the outside of splitter 140 into the hot region radially inward of the splitter duct 140 where the products of combustion from combustion chamber 60 flow, thus triggering the mixing pattern downstream of the splitter duct plane. This FIG. 38 construction will set up helical spinning layers of hot and cold air to mix downstream of the splitter duct. While but a single row of such scooped slots are shown in FIG. 38, it should be realized that more than one row or a pattern thereof could be used, as is shown in FIG. 35 without scoops.

For improved acoustic properties and for improved combustion of the trigger 166, it is recommended that trigger 166 be made of sheet metal with a series of small holes 257 therein and preferably, scoop member 259 (see FIG. 45) to be associated with holes 257 to force small jets from the cold side of the trigger to flow to the hot side to cool the trigger and to also introduce a fine scale of disturbance or turbulence to improve combustion.

As mentioned previously, acoustic benefit can be gained by utilizing perforations in the corrugated trigger of the type shown in FIG. 14 and this is important because large amplitude noise has been shown to affect combustion efficiency adversely. Additional noise suppression can be achieved by varying the height and width (distance between) of the trigger corrugations or other trigger mechanisms, and also varying the cycle of the trigger pattern peripherally to achieve noise suppression, thus producing spiraling or helical sheets of hot and cold gases having different frequency responses. Such a configuration is depicted in FIG. 39 wherein It represents height or amplitude of the convolutions and l and m represent different corrugation widths.

An engine of the type in which my invention may be used is shown in FIG. 13 as turbine engine 40, which consists of a compressor section 42, a burner or combustion section 44, a turbine section 46, and may have an afterburner section 48, which terminates in a variable area nozzle 50. Engine 40 is preferably of circular cross-section and concentric about axis 52. Combustion section 44 includes outer casing 54 and and annular combustor combustion chamber or burner 56, which consists of diffuser inlet section 58, combustion zone 60 and dilution zone 62. As used herein, the term annular combustion chamber means a combustion chamber having an annular passage extending from the inlet, or upstream end, to the outlet, or downstream end thereof. Fuel is supplied to combustor 56 by variable output fuel pump 64 which is either under pilot manual or pilot set automatic control, and is fed into the inlet of combustor 56 in a fashion to be described hereinafter, to be mixed therewith with a portion of the pressurized gas from compressor section 42 to form a combustible fuel-air mixture to be burned in combustion zone 60, from which the products of combustion pass into dilution zone 62 for mixing with diluent cooling air also from the compressor to lower the temperature thereof prior to entry into turbine section 46. Engine 40 may be of the type more fully described in U.S. Pat. Nos. 2,747,367, 2,711,63l and 2,846,841.

A typical combustor system or section 44 of a turbine engine of the type shown in FIG; 13 may be considered to be composed of two components in series, namely, a combustion zone 60 in which fuel is burned in a portion of the total engine airflow from the compressor and a dilution zone 62 in which the balance of the airflow is mixed with the hot products ofcombustion from the combustion zone so that a substantially cooler mixture than the products of combustion is passed through the turbine 46. Any combination of concentric mixtures, barberpole mixers, and bent tube mixers, can be used to perform the combustion zone region mixing and combustion function and the dilution zone region mixing and cooling functions of such a combustion section 44.

Referring to FIG. 14 we see annular combustion chamber 56 which comprises outer case 54 and inner case 1 13, which are preferably of circular cross-section and mounted concentrically about axis or centerline 16. The air from the compressor section 42 of FIG. 13 enters annular inlet 114 in either swirling flow or nonswirling flow depending upon the discharge conditions from the compressor section 42, and portions thereof pass through pilot passage 124, main combustion zone fuel preparation passage 126 and the diluent air passage 130. Further quantities of airflow through passages 122 and 132 to provide for cooling the walls of the combustor chamber. Vanes 116, 118, and 128 are employed as required to swirl or straighten the flow in the respective passage so as to satisfy the previously defined mixing instability criteria. Each of the passages 122, 124, 126, 130 and 132 are of annular shape since the outer burner liner 134, the inner burner liner 136 and splitter ducts 138 and 140 are of circular crosssection and concentric about axis 16. Turning vanes 116 and 118, 120 and 128 may be fixed or any or all vanes could be of the variable angle type as shown, for example, in FIG. 15 wherein each of vanes 116 is pivotally connected to duct 134 and outer housing 54 by pivot pins 144 and 146, respectively. Pivot pin 146 extends through outer case 54 and carries ring gear 148 at its outer end, which engages circumferentially rotatable ring or annular gear 150, which is pilot operated to rotate circumferentially about axis 16 by motion of pilot actuated lever 152 into and out of the plane of the paper, thereby causing vanes 116 to rotate in unison and thereby vary the tangential velocity V, of the gas or fluid passing thereby. The swirling air which entered passage 124 has atomized fuel added thereto by fuel injection device 156 to form a fuel-air mixture which is ignited by ignitor 158 and vitiated in pilot combustion chamber 160 which is located downstream of aperturetype flameholder 161, which is a tilted and apertured plate extending between ducts 134 and 138. The hot swirling stream emerging from passage 124 serves as a pilot stream for combustion chamber 60. The swirling air entering passage 126 has atomized fuel added thereto by injection member 162 and the amount of fuel to be discharged into passage 124 and 126 can be regulated by the size and number of fuel nozzles, such as 162 located therein and by pilot controlled valves 163 and 165 located in the fuel line thereto. The atomized fuel entering passage 126 mixes with the swirling gas passing therethrough to provide a combustible fuelair mixture to combustion chamber 60 for accelerated mixing pilot stream emerging from passage 124 and subsequent combustion of this flow. It will accordingly be seen that hot swirling pilot stream emerging from passageway 124 to mix with and sustain combustion in the fuel-air mixture emerging from passageway 126 and the thermodynamic and aerodynamic characteristics of these two streams are established so as to satisfy the 

1. A combustion chamber including a duct adapted to define a passage through which at least two fluids flow in swirling sideby-side relationship to establish an interface therebetween with one of said fluids having a density Rho 1 and a tangential velocity Vt1 and another of said fluids having a density Rho 2 and a tangential velocity Vt2, means to vary the product parameter Rho Vt2 of one of said fluids to accelerate intermixing therebetween, and including trigger means shaped to initiate interdigitated substantially radially inwardly and substantially radially outwardly sheet flow between the two fluids to physically disturb the interface between the two fluids.
 2. a plurality of apertures extending through the walls of the ring means to permit some of the fuel-air mixture from the annular passage to pass therethrough into the protected interior chamber of said flame-holder mechanism, D. ignitor means operatively associated with said flame-holder mechanism to ignite the portion of the fuel-air mixture entering the interior protected chamber of said flameholder mechanism through said apertures to form a combusting fluid to serve as a pilot flame to continuously ignite said swirling fuel-air mixture to burn in said primary combustion zone, and E. and having a dilution zone downstream of said primary combustion zone and including means to dilute and cool the products of combustion from said primary combustion zone in said dilution zone.
 2. a splitter duct of circular cross-section positioned between said inner and outer ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said inner and outer ducts,
 2. a plurality of apertures extending through the walls of the ring means to permit some of the fuel-air mixture from the annular passage to pass therethrough into the protected interior chamber of said flame-holder mechanism, D. ignitor means operatively associated with said flameholder mechanism to ignite the portion of the fuel-air mixture entering the interior protected chamber of said flameholder mechanism through said apertures to form a combusting fluid to serve as a pilot flame to continuously ignite said swirling fuel-air mixture to burn in said primary combustion zone.
 2. wherein said products of combustion and said fourth fluid mix in said dilution zone to form a fifth fluid of density Rho 5 and tangential velocity Vt5 and wherein said outer wall member of said dilution zone mixer includes a plurality of axially and radially spaced duct members which axially overlap, and including a cascade of turning vanes positioned in at least one of said overlapping duct areas, and including means to pass cooling fluid of density Rho 6 through said vane cascade, and with the vanes of the cascade oriented so as to impart a tangential velocity Vt6 to the coolant flowing therethrough so as to produce a product parameter Rho 6 Vt62> Rho 5 Vt52, and
 2. Apparatus according to claim 1 wherein said duct is of circular cross-section and including means to cause said fluids to flow in coannular side-by-side relationship.
 2. a first duct member of circular cross-section positioned in said first annular passage coaxially with said wall members and cooperating with said inner wall member to define a second annular passage therebetween and converging toward said inner wall member in a downstream direction,
 2. wherein said products of combustion and said fourth fluid mix in said dilution zone to form a fifth fluid of density Rho 5 and tangential velocity Vt5 and wherein said outer wall member of said dilution zone mixer includes a plurality of axially and radially spaced duct members which axially overlap, and including a cascade of turning vanes positioned in at least one of said overlapping duct areas, and including means to pass cooling fluid of density Rho 6 through said vane cascade, and with the vanes of the cascade oriented so as to impart a tangential velocity Vt6 to the coolant flowing therethrough so as to produce a product parameter Rho 6 Vt62> Rho 5 Vt52.
 2. wherein in said combustion zone mixer said second fluid is a fuel-air mixture, and including means to inject and combust fuel in said second annular passage to establish a pilot fuel combustion zone therein so that said first fluid is the combusting fuel-air mixture from said pilot fuel combustion zone, and so that said first fluid mixes with said second fluid to burn in said primary combustion zone to produce said products of combustion and, further, wherein in said dilution zone mixer, said second annular passage is the passage through which said products of combustion flow to said dilution zone, and wherein said fourth fluid is a diluent which flows through said third annular passage into said diluent zone for mixing with and cooling of said products of combustion therein.
 2. a first duct member of circular cross-section positioned in said fourth annular passage coaxially with said wall members and cooperating with said inner wall member to define a fifth annular passage therebetween,
 2. a first duct member of circular cross-section positioned in said fourth annular passage coaxially with said wall members and cooperating with said inner wall member to define a fifth annular passage therebetween,
 3. a second duct member of circular cross-section positioned coaxially with said wall members and positioned between said first duct member and said outer wall member and cooperating with said outer wall member to define a sixth annular passage therebetween and to define a seventh annular passage with said first duct member, and enveloping the dilution zone,
 3. a second duct member of circular cross-section positioned coaxially with said wall members and positioned between said first duct member and said outer wall member and cooperating with said outer wall member to define a sixth annular passage therebetween and to define a seventh annular passage with said first duct member, and enveloping the diluent zone,
 3. wherein said inner wall member of said dilution zone mixer includes a plurality of axially and radially spaced duct members which overlap axially and further including at least one vaned cascade in at least one of said overlapping stations, and further including means to pass a coolant of density Rho 7 through said one overlapping station and with the vanes of said cascade oriented so as to establish a tangential velocity Vt7 in the coolant passing therethrough so as to establish the product parameter relationship Rho 7 Vt72< Rho 5 Vt52.
 3. Apparatus according to claim 1 and wherein said means constitutes apparatus for varying the density, Rho , of one of said fluids.
 3. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1,
 3. a second duct member of circular cross-section positioned coaxially with said wall members and positioned between said first duct member and said outer wall member and cooperating with said outer wall member to define a third annular passage therebetween and converging toward said outer wall member in a downstream direction and cooperating with first duct member to define a divergent annular passage therebetween enveloping a primary combustion zone,
 4. Apparatus according to claim 1 and wherein said means constitutes means to vary the tangential velocity, Vt, of one of said fluids.
 4. at least one row of helically directed and circumferentially oriented slots extending through said second duct member to place said third annular passage into communication with said divergent annular passage,
 4. at least one row of helically directed and circumferentially oriented slots extending through said second duct member to place said sixth annular passage into communication with said seventh annular passage,
 4. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Rho Vt2 so that the product parameter Rho 2 Vt2 > Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct for mixing and combusting therein to form a third fluid which is the product of combustion. B. said dilution zone including a barberpole mixer having:
 4. at least one row helically directed and circumferentially oriented slots extending through said second duct member to place said sixth annular passage into communication with said seventh annular passage,
 5. at least one row of helically directed and circumferentially oriented slots extending through said first duct member to place said fifth annular passage into communication with said seventh annular passage,
 5. at least one row of helically directed and circumferentially oriented slots extending through said first duct member to place said second annular passage into communication with said diverging annular passage,
 5. at least one row of helically directed and circumferentially oriented slots extending through said first duct member to place said fifth annular passage into communication with said seventh annular passage,
 5. Apparatus according to claim 1 wherein said combustion chamber is an annular combustion chamber and wherein said flow path of said two fluids is coannular.
 6. Apparatus according to claim 1 wherein the flow paths of said two fluids is about a common center of curvature.
 6. means to pass said fourth fluid of density Rho 4 through said seventh annular passage at a tangential velocity Vt4,
 6. means to pass said third fluid of density Rho 3 through said seventh annular passage at a tangential velocity Vt3,
 6. means to pass a first swirling fluid of density Rho 1 through said diverging annular passage at a tangential velocity Vt1,
 7. means to pass fourth fluid through said fifth annular passage and through said slots in said first duct member to enter said seventh annular passage at density Rho 4 and tangential velocity Vt4 so that the product parameter Rho 3 Vt32 of the third fluid is less than the product parameter Rho 4 Vt42 of the fourth fluid to accelerate intermixing between said third and fourth fluids and,
 7. means to pass second fluid through said second annular passage and through said slots in said first duct member to enter said divergent annular passage at density Rho 2 and tangential velocity Vt2 so that the product parameter Rho 1 Vt12 of the first fluid is less than the product parameter Rho 2 Vt22 of the second fluid to accelerate intermixing between said first and second fluids, and
 7. means to pass fluid through said fifth annular passage and through said slots in said first duct member to enter said seventh annular passage at density Rho 5 and tangential velocity Vt5 so that the product parameter Rho 4 Vt42 of the fourth fluid is less than the product parameter Rho 5 Vt52 of the fifth fluid to accelerate intermixing between said fourth and fifth fluids and,
 7. An annular combustion chamber including: A. inner and outer ducts of substantial circular cross section positioned coasially to define a first annular passage therebetween, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Vt2 to that the product parameter Rho 2Vt22 > Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct, E. including trigger means located at the downstream end of said splitter duct to disturb the unstable interface between the two fluids and accelerate mixing therebetween, and F. wherein said trigger means is a ring member connected to the downstream edge of said splitter duct and shaped To define helical corrugations of maximum amplitude at its downstream end.
 8. An annular combustion chamber including: A. inner and outer ducts of substantial circular cross section positioned coaxially to define a first annular passage therebetween, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Vt2 so that the product parameter Rho 2 Vt22 > Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct, E. including trigger means located at the downstream end of said splitter duct to disturb the unstable interface between the two fluids and accelerate mixing therebetween, F. wherein said trigger means is a ring member connected to the downstream edge of said splitter duct and shaped to define helical corrugations of maximum amplitude at its downstream end, and G. wherein said helical corrugations vary in both amplitude and width.
 8. means to pass a third fluid through said third annular passage and through said helical slots in said second duct member to enter said diverging annular passage at density Rho 3 and tangential velocity Vt3 and so that the product parameter Rho 3 Vt3 2 of the third fluid is less than the product parameter Rho 1 Vt1 2 of the first fluid to accelerate mixing between said first and third fluids and so that said first, second and third fluids mix and combust to form a fourth fluid of density Rho 4 and tangential velocity Vt4 in said divergent annular passage. B. a dilution zone mixer having:
 8. means to pass a fifth fluid through said sixth annular passage and through said helical slots in said second duct member to enter said seventh annular passage at density Rho 5 and tangential velocity Vt5 and so that the product parameter Rho 5 Vt52 of the third fluid is less than the product parameter Rho 4 Vt42 of the fourth fluid to accelerate mixing between said third and fifth fluids.
 8. means to pass a sixth fluid through said sixth annular passage and through said helical slots in said second duct member to enter said seventh annular passage at density Rho 6 and tangential velocity Vt6 and so that the product parameter Rho 6 Vt6 2 of the sixth fluid is less than the product parameter Rho 4 Vt42 of the fourth fluid to accelerate mixing between said fourth and sixth fluids.
 9. An annular combustion chamber including: A. inner and outer ducts of substantial circular cross section positioned coaxially to define a first annular passage therebetween, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Vt2 so that the product parameter Rho 2 Vt22 > Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct, and E. including means to inject fuel into said third annular passage so that the second fluid is a fuel-air mixture entering said first annular passage downstream of said splitter duct, and means to inject fuel and support combustion thereof in said second annular passage so that said first fluid are the hot products of combustion zone to mix with and ignite the fuel-air mixture from the third passage in said first annular passage downstream of said splitter duct.
 10. An annular combustion chamber having a combustion zone and a dilution zone axially spaced therein and wherein the combustion zone includes a concentric mixer and the dilution zone includes a concentric mixer and wherein said combustion zone concentric mixer comprises: A. inner and outer ducts of substantial circular cross section positioned coaxially to define a first annular passage therebetween, enveloping the primary combustion zone, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and secOnd ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Vt2, so that the product parameter Rho 2 Vt22> Rho 1 Vt12 to thereby establish an unstable interface between said fluids in siad first annular passage downstream of said splitter duct for mixing therein to form a combustible third fluid whose products of combustion are of density Rho 3 and tangential velocity Vt32,
 11. An annular combustion chamber having a combustion zone and a dilution zone axially spaced therein and wherein the combustion zone includes a concentric mixer and the dilution zone includes a concentric mixer and wherein said combustion zone concentric mixer comprises: A. inner and outer ducts of substantial circular cross section positioned coaxially to define a first annular passage therebetween, enveloping the primary combustion zone, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a seleCted tangential velocity Vt2, so that the product parameter Rho 2 Vt22> Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct for mixing therein to form a combustible third fluid whose products of combustion are of density Rho 3 and tangential velocity Vt32,
 12. An annular combustion chamber having a combustion zone and a dilution zone axially spaced therein and wherein the combustion zone includes a concentric mixer and the dilution zone includes a concentric mixer and wherein said combustion zone concentric mixer comprises: A. inner and outer ducts of substantial circular cross section positioned coaxially to define a first annular passage therebetween, enveloping the primary combustion zone, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Vt2, so that the product parameter Rho 2 Vt22> Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct for mixing therein to form a combustible third fluid whose products of combustion are of density Rho 3 and tangential velocity Vt32,
 13. An annular combustion chamber concentric about an axis and having a combustion zone located axially forward or upstream of a dilution zone and including: A. inner and outer duct members of circular cross section and positioned coaxially about said axis and shaped to define a diverging annular passage therebetween increasing in cross-sectional area in a downstream direction and communicating with the primary combustion zone at its downstream end, B. means to pass a swirling fuel-air mixture of density Rho 1 through said diverging annular passage at tangential velocity Vt1, C. a combination flameholder and mixing trigger mechanism located in said annular passage between the inlet thereof and the primary combustion zone and attached to the outer duct member and comprising a convoluted ring with convolutions increasing in a downstream direction and extending around the periphery of said annular passage and with said convolutions being in substantially helical shape to substantially assume the direction of flow of the fuel-air mixture passing through the annular passage and including a plurality of apertures on the walls thereof to permit some of the fuel-air mixture from the annular passage to pass therethrough into the interior of said flameholder mechanism, D. ignitor means operatively associated with said flame-holder and triggEr mechanism to ignite the portion of the fuel-air mixture entering the interior of said flameholder mechanism through said apertures to form a combusting fluid of density Rho 2 and having a tangential velocity Vt2 imparted thereto by the convolutions of the flameholder to establish the product parameter relationship Rho 2 Vt22 is less than Rho 1 Vt12 so as to establish an unstable and convoluted interface between the fuel-air mixture of the annular passage and the products of combustion so as to accelerate mixing and combustion therebetween in said primary combustion zone, and E. and having a dilution zone downstream of said primary combustion zone and including means to dilute and cool the products of combustion from said primary combustion zone in said dilution zone.
 14. A combustion mechanism including: A. a substantially cylindrical duct, B. means to cause two fluids to pass through said duct in swirling motion to establish an interface therebetween and, to establish a density Rho 1 and tangential velocity Vt1 in one of said fluids and a density Rho 2 and a tangential velocity Vt2 in the other of the fluids and, C. means to vary the product parameter Rho Vt2 of one of said fluids to affect mixing therebetween, and D. trigger means located in and shaped to vary the shape of the interface to accelerate mixing between the two fluids by initiating interdigitated substantially radially inwardly and substantially radially outwardly sheet flow between the two fluids.
 15. Combustion mechanism including: A. a first substantially cylindrical duct, B. a second substantially cylindrical duct positioned within the first duct and defining an annular passage therebetween and a second passage therewithin, and terminating short of said first duct, C. means to pass a first swirling fluid through said annular passage, D. means to pass second swirling fluid through the second passage, E. means to establish a selected product parameter Rho 1 Vt12 in the first swirling fluid, where Rho 1 is density and Vt12 is tangential velocity, F. means to establish a selected product Rho 2 Vt22 in the second swirling fluid which is greater than product parameter Rho 1 Vt12 to promote mixing between the two fluids downstream of the second cylindrical duct, and G. means to alter the shape of interface between the two fluids downstream of the cylindrical duct by establishing interdigitated radial inward and radial outward flow between the two fluids to accelerate mixing therebetween.
 16. A combustion mechanism including: A. a substantially cylindrical duct, B. separating means establishing two flow paths in said duct and terminating within said duct, C. means to pass a fluid through the first of said flow paths in swirling motion and to establish a density Rho 1 and a tangential velocity Vt1 in the fluid, D. means to pass a second fluid through another flow path and to establish a density Rho 2 and a tangential velocity Vt2 in the other of said fluids so that said fluids are separated passing through said duct in the region of said separating means and so that said fluids are not separated when passing through said duct downstream of said separating means so that an interface is established therebetween and so that the difference in the product Rho Vt2 of the two fluids accelerates mixing therebetween at the interface, and E. trigger means operatively associated with said separating means and shaped to disturb the interface and accelerate mixing by establishing substantially radially inwardly and substantially radially outwardly interdigitated flow patterns between said fluids.
 17. An annular combustion chamber including: A. inner and outer ducts Of substantial circular cross section positioned coaxially to define a first annular passage therebetween, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Vt2 so that the product parameter Rho 2 Vt22> Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct, and E. trigger means located at the downstream end of said splitter duct and shaped to disturb the interface and accelerate mixing by extablishing substantially radially inwardly and substantially radially outwardly interdigitated flow patterns between said fluids.
 18. A combustion chamber fluid mixer including a combustion chamber duct of substantially circular cross section, means to pass a first fluid of density Rho 1 through said duct in a swirling flow path having a tangential velocity Vt1, means to pass a second fluid of density Rho 2 through said duct in a swirling flow path having a tangential velocity Vt2 and in side-by-side relationship with the flow path of the first fluid to establish an interface therebetween so that the product parameter Rho 1 Vt12 is different from the product parameter Rho 2 Vt22 to accelerate mixing between the two fluids, and trigger means shaped to disturb the interface and accelerate mixing by establishing substantially radially inwardly and substantially radially outwardly interdigitated flow patterns between said fluids.
 19. A combustion chamber including: A. combustion chamber enclosure means of circular cross section, B. means to pass a first fluid of density Rho 1 through said enclosure means and to establish a tangential velocity Vt1 in said first fluid, C. means to pass a second fluid of density Rho 2 through said enclosure means and to establish a tangential velocity Vt2 in said second fluid so that two fluids are flowing in swirling fashion in side-by-side relationship to establish an interface therebetween, and wherein the product parameter Rho 1 Vt12 is different than the product parameter Rho 2 Vt22 so as to accelerate intermixing between the two fluids, and trigger means shaped to disturb the interface and accelerate mixing by establishing substantially radially inwardly and substantially radially outwardly interdigitated flow patterns between said fluids.
 20. An annular combustion chamber having a combustion zone and a dilution zone axially spaced therein and wherein the combustion zone includes a concentric mixer and the dilution zone includes a concentric mixer and wherein said combustion zone concentric mixer comprises: A. inner and outer ducts of substantial circular cross-section positioned coaxially to define a first annular passage therebetween, enveloping the primary combustion zone, B. a splitter duct of circular cross-section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first flUid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Rho Vt2, so that the product parameter Rho 2 Vt2 > Rho 1 Tt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct for mixing therein to form a combustible third fluid whose products of combustion are of density Rho 3 and tangential velocity Vt32.
 21. Apparatus according to claim 20 and including trigger means operatively associated with the downstream end of said combustion zone mixer splitter duct and said dilution zone mixer splitter duct to physically distort the interface of the fluids joining downstream of these splitter ducts, and shaped to disturb the interfaces and accelerate mixing by establishing substantially radially inwardly and substantially radially outwardly interdigitated flow patterns between said fluids.
 22. The method of mixing and combusting in a combustion chamber comprising the steps of: A. causing a first fluid of selected combustible characteristics and of density Rho 1 to flow in the combustin chamber at tangential velocity Vt1, B. causing a second fluid of selected combustible characteristics which will permit said two fluids to combust when mixed and of density Rho 2 to flow in the combustion chamber at tangential velocity Vt2 in side-by-side relationship with the first fluid so as to establish an interface therebetween and wherein product parameter Rho 1 Vt12 is greater than the product parameter Rho 2 Vt22 so that said interface is unstable and so that mixing between the fluids is accelerated, and including the additional step of disturbing the unstable interface to establish interleaved, helical sheet flow between said fluids.
 23. An annular combustion chamber concentric about an axis and having a primary combustion zone and including: A. inner and outer duct members of circular cross section and positioned coaxially about said axis and shaped to define an annular passage therebetween and communicating with the primary combustion zone at its downstream end, B. means to pass a swirling fuel-air mixture through said annular passage with both tangential and axial velocity about said axis, C. a combustion flameholder mechanism located in said annular passage between the inlet thereof and the primary combustion zone and comprIsing:
 24. An annular combustion chamber having a combustion zone including a concentric mixer comprising: A. inner and outer ducts of substantial circular cross section positioned coaxially to define a first annular passage therebetween, enveloping the primary combustion zone, B. a splitter duct of circular cross section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fuel-air mixture through said second annular passage with said first fuel-air mixture having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to ignite said first fuel-air mixture and establish a pilot combustion zone in said second annular passage to produce combustion or products of combustion having a density of Rho 3 and tangential velocity Vt3 entering said first annular passage from said second annular passage, and E. means to pass a second fuel-air mixture, dissimilar to said first fuel-air mixture, through said third annular passage and with said second fuel-air mixture having a selected density Rho 2 and a selected tangential velocity Rho Vt2, so that the product parameter Rho 2 Vt2 > Rho 3 Vt32 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct for accelerated mixing and combustion therebetween.
 25. The method of mixing and combusting in a combustion chamber comprising the steps of: A. causing a first fluid of selected combustible characteristics and of density Rho 1 to flow in the combustion chamber at tangential velocity Vt1, B. causing a second fluid of selected combustible characteristics which will permit said two fluids to combust when mixed and of density Rho 2 to flow in the combustion chamber at tangential velocity Vt2 in coaxial annular side-by-side relationship and within the first fluid so as to establish an interface therebetween and wherein product parameter Rho 2 Vt22 is greater than the product parameter Rho 1 Vt12 so that said interface is unstable and so that mixing between the fluids is accelerated.
 26. The method according to claim 25 wherein said first fluid is a combustible fuel-air mixture and said second fluid is a pilot fluid.
 27. The method according to claim 25 wherein said first fluid is air and wherein said second fluid is a fuel-rich vitiated air mixture derived by adding fuel to vitiated products of combustion.
 28. A combustion chamber including a duct adapted to define a passage through which at leAst two fluids flow in swirling side-by-side relationship to establish an interface therebetween with one of said fluids having a density Rho 1 and a tangential velocity Vt1 and another of said fluids having a density Rho 2 and a tangential velocity Vt2, means to establish the product parameter Rho Vt2 of one of said fluids to be different than the corresponding product parameter Rho Vt2 of the other fluid to accelerate intermixing therebetween and including trigger means to physically disturb the interface and establish interdigitated substantially radially inwardly and substantially radially outwardly sheet flow between said two fluids.
 29. Apparatus according to claim 15 wherein the following mixing criteria exists: Rho 2 Vt22 > Rho 1 Vt12.
 30. Apparatus according to claim 7 and including apertures in said corrugated trigger.
 31. Apparatus according to claim 7 and including scoop means operatively connected to the corrugations of said trigger and shaped to intercept the flow of one of said fluids and cause it to pass through said aperture to effect trigger means cooling and to increase the rate of mixing between the two fluids.
 32. Apparatus according to claim 17 wherein said trigger means constitutes a plurality of vortex generators in the form of selectively contoured vaned members positioned circumferentially about the periphery of said splitter duct at the after end thereof and extending into at least one of said first and second annular passages.
 33. Apparatus according to claim 32 wherein the curvature of adjacent vortex generator vanes is opposite.
 34. Apparatus according to claim 33 wherein said vortex generators constitute at least one circumferentially positioned rows of vanes.
 35. Apparatus according to claim 17 wherein said trigger means comprises a circumferentially oriented plurality of helically shaped slot members forming the downstream end of said splitter duct.
 36. Apparatus according to claim 35 wherein said helical slots extend in the direction of flow of at least one of said fluids.
 37. Apparatus according to claim 17 and wherein said trigger means comprises at least two axially spaced circumferentially oriented rows of helical slots located at the downstream end of said splitter duct and oriented or extended in the direction of flow of at least one of said fluids.
 38. Apparatus according to claim 17 wherein said trigger means is a helically corrugated ring forming the downstream end of said splitter duct and having helically shaped slots therein with both the corrugations and the slots extending substantially in the direction of flow of one of said fluids.
 39. Apparatus according to claim 36 and including scoop means connected to said helical slots and shaped to project into one of said first or second passages to intercept fluid passing therethrough and to direct that fluid through its associated helical slot.
 40. Apparatus according to claim 17 wherein said second fluid is air and including apparatus to inject fuel into said second passage and to support combustion thereof a sufficient distance forward of the downstream end of said splitter duct so that said initially injected fuel is substantially fully vitiated forward of said downstream end of said splitter duct, and further including second means to inject fuel into said second passage forward of the downstream end of said splitter duct to mix with and be heated by the fully vitiated products of combustion therein so that said second fluid comprises a combustible fuel-air mixture of said substantially vitiated products of combustion and said fuel injected by said second fuel injection means so that said first and second fluids will mix and combust in said first passage downstream of said splitter duct.
 41. Apparatus according to claim 18 wherein said first fluid is a combustible fuel-air mixture.
 42. An annular combustion chamber inCluding: A. inner and outer wall member of circular cross-section and concentric about an axis to define a first annular passage therebetween. B. a first duct member of circular cross-section positioned in said first annular passage coaxially with said wall members and cooperating with said inner wall members to define a second annular passage therebetween, C. a second duct member of circular cross-section positioned coaxially with said wall members and positioned between said first duct member and said outer wall member and cooperating with said outer wall member to define a third annular passage therebetween and cooperating with said duct member to define a divergent annular passage therebetween, D. at least one row of helically directed and circumferentially oriented slots extending through said second duct member to place said third annular passage into communication with said divergent annular passage. E. at least one row of helically directed and circumferentially oriented slots extending through said first duct member to place said second annular passage into communication with said diverging annular passage, F. means to pass first swirling fluid of density Rho 1 through said diverging annular passage at a tangential velocity Vt1, G. means to pass second fluid through said second annular passage and through said slots in said first duct member to enter said divergent annular passage at density Rho 2 and tangential velocity Vt2 so that the product parameter Rho 1 Vt12 of the first fluid is less than the product parameter Rho 2 Vt22 of the second fluid to accelerate intermixing between said first and second fluids, and H. means to pass a third fluid through said third annular passage and through said helical slots in said second duct member to enter said diverging annular passage at density Rho 3 and tangential velocity Vt3 and so that the product parameter Rho 3 Vt32 of the third fluid is less than the product parameter Rho 1 Vt12 of the first fluid to accelerate mixing between said first and third fluids.
 43. Apparatus according to claim 42 and including flow directing guide vanes operatively associated with the slots in said first and second duct members to assist in achieving the desired product parameter Rho Vt2 to accelerate fluid intermixing.
 44. Apparatus according to claim 42 wherein said first fluid is a fuel-air mixture and wherein said second and third fluids are secondary flow air.
 45. Apparatus according to claim 42 wherein said first fluid is a burning fuel-air mixture serving as a pilot flame and including means to inject atomized fuel into said second and third annular passages so that said second and third fluids are combustible fuel-air mixture which mix with and are ignited by said pilot flame for combustion in said divergent annular passage.
 46. Apparatus according to claim 42 wherein said second and third fluids are air and wherein said first and second duct members are cylinders at their forward ends and diverge at their after ends to cooperate to form an annular passage therebetween with parallel side walls at its forward end and said divergent annular passage at its after end, and further including first fuel injection means and combustion supporting means located in said parallel walled annular passage at a station forward of said divergent annular passage so that products of combustion are substantially fully vitiated upstream thereof, and still further including means to inject fuel into said substantially vitiated products of combustion in said parallel walled annular chamber so that said first fluid entering said divergent annular chamber consists of a heated mixture of the atomized fuel and the vitiated products of combustion which ignite and burn with said first and second fluids in said divergent annular passage.
 47. Apparatus acCording to claim 42 wherein said inner and outer wall members are substantially cylindrical in shape and wherein said first and second duct members are cylindrical in shape at their forward ends and diverge from one another at their after end at the station of the slots so that said first and second duct members cooperate to define an annular passage with parallel walls at their forward end and said annular divergent passage at their after ends and so that said second and third annular passages are convergent at their after ends in the vicinity of the slot station.
 48. Apparatus according to claim 40 and including means to inject atomized fuel into said annular passage with parallel walls and to support combustion thereof in said annular, parallel walled passage so that said first fluid entering said divergent annular passage is a combusting fuel-air mixture.
 49. An annular combustion chamber having a combustion zone and a dilution zone axially spaced therein and wherein the combustion zone includes a concentric mixer and the dilution zone includes a concentric mixer and wherein said combustion zone concentric mixer comprises: A. inner and outer ducts of substantial circular cross-section positioned coaxially to define a first annular passage therebetween, enveloping the primary combustion zone, B. a splitter duct of circular cross-section positioned between said first and second ducts and cooperating therewith to define a second annular passage radially outward thereof and a third annular passage radially inward thereof and having a downstream end terminating short of said first and second ducts, C. means to pass a first swirling fluid through said second annular passage with said first fluid having a selected density Rho 1 and a selected tangential velocity Vt1, D. means to pass a second fluid, dissimilar to said first fluid, through said third annular passage and with said second fluid having a selected density Rho 2 and a selected tangential velocity Vt2 so that the product parameter Rho 2 Vt2 > Rho 1 Vt12 to thereby establish an unstable interface between said fluids in said first annular passage downstream of said splitter duct for mixing therein to form a combustible fluid.
 50. Apparatus according to claim 20 and including means to cool said inner and outer ducts of said combustion zone and said dilution zone mixers.
 51. Apparatus according to claim 20 and including a circumferentially extending vane cascade located at the upstream end of said second and third annular passage of said combustion zone mixer and said third annular passage of said dilution zone mixer and which vanes are selectively oriented to produce the desired tangential velocity Vt of the fluid passing into their respective annular passages.
 52. Apparatus according to claim 51 wherein at least one of said vane cascades is of the variable positionable variety.
 53. An annular combustion chamber which is concentric about an axis and includes a combustion zone and dilution zone axially spaced therefrom, said combustion zone having radially staged mixing therein and including: A. a combustion zone mixer having:
 54. An annular combustion chamber which is concentric about an axis and includes a combustion zone and a dilution zone axially spaced therefrom, said combustion zone including a combustion zone mixer having: A. inner and outer wall members of circular cross-section and concentric about said axis to define a first annular passage therebetween, B. a first duct member of circular cross-section positioned in said first annular passage coaxially with said wall members and cooperating with said inner wall member to define a second annular passage therebetween and converging toward said inner wall member in a downstream direction, C. a second duct member of circular cross-section positioned coaxially with said wall members and positioned between said first duct member and said outer wall member and cooperating with said outer wall member to define a third annular passage therebetween and converging toward said outer wall member in a downstream direction and cooperating with first duct member to define a divergent annular passage therebetween, D. at least one row of helically directed and circumferentially oriented slots extending through said second duct member to place said third annular passage into communication with said divergent annular passage, E. at least one row of helically directed and circumferentially oriented slots extending through said first duct member to place said second annular passage into communication with said diverging annular passage, F. means to pass a first swirling fluid of density Rho 1 through said diverging annular passage at a tangential velocity Vt1, G. means to pass second fluid through said second annular passage and through said slots in said first duct member to enter said divergent annular passage at density Rho 2 and tangential velocity Vt2 so that the product parameter Rho 1 Vt12 of the first fluid is less than the product parameter Rho 2 Vt2 2 of the second fluid to accelerate intermixing between said first and second fluids at a first stage, and, H. means to pass a third fluid through said third annular passage and through said helical slots in said second duct member to enter said diverging annular passage at density Rho 3 and tangential velocity Vt3 and so that the product parameter Rho 3 Vt32 of the third fluid is less than the product parameter Rho 1 Vt1 2 of the first fluid to accelerate mixing between said first and third fluids at a second stage radially displaced from said first stage and so that said first, second and third fluids mix to form a fourth fluid of density Rho 4 and tangential velocity Vt4 in said divergent annular passage.
 55. An annular combustion chamber which is concentric about an axis and includes a combustion zone and a dilution zone axially spaced therefrom, said dilution zone including a dilution zone mixer having: A. inner and outer wall members of circular cross-section and concentric about an axis to define a first annular passage therebetween, B. a first duct member of circular cross-section positioned in said first annular passage coaxially with said wall members and cooperating with said inner wall member to define a second annular passage therebetween, C. a second duct member of circular cross-section positioned coaxially with said wall members and positioned between said first duct member and said outer wall member and cooperating with said outer wall member to define a third annular passage therebetween and cooperating with first duct member to define a fourth annular passage therebetween, D. at least one row of helically directed and circumferentially oriented slots extending through said second duct member to place said third annular passage into communication with said fourtH annular passage, E. at least one row of helically directed and circumferentially oriented slots extending through said first duct member to place said second annular passage into communication with said fourth annular passage, F. means to pass a first swirling fluid of density Rho 1 through said fourth annular passage at a tangential velocity Vt1, G. means to pass second fluid through said second annular passage and through said slots in said first duct member to enter said fourth annular passage at density Rho 2 and tangential velocity Vt2 so that the product parameter Rho 1 Vt12 of the first fluid is less than the product parameter Rho 2 Vt2 2 of the second fluid to accelerate intermixing between said first and second fluids at a first stage and, H. means to pass a third fluid through said third annular passage and through said helical slots in said second duct member to enter said fourth annular passage at density Rho 3 and tangential velocity Vt3 and so that the product parameter Rho 3 Vt3 2 of the third fluid is less than the product parameter Rho 1 Vt1 2 of the first fluid to accelerate mixing between said first and third fluids at a second stage spaced radially from said first stage.
 56. Apparatus according to claim 53 and wherein the row of helical slots in the second duct member of said combustion zone mixer and said dilution zone mixer are oppositely directed to the slots in the row of helical slots in the first duct member of said combustion zone mixer and said dilution zone mixer.
 57. Apparatus according to claim 53 wherein said first fluid is a combusting mixture, wherein said second and third fluids are combustible fuel-air mixtures which interdigitate and mix at an accelerated rate with said first fluid in said combustion zone and wherein said fourth fluid is the product of combustion from said combustion zone and wherein said fifth and sixth fluids are diluents which mix at an accelerated rate with and cool said fourth fluid in said dilution zone.
 58. Apparatus according to claim 57 wherein said first and second duct members of said combustion zone mixer are cylindrical members at their upstream ends to define an annular passageway having parallel side walls and are divegent at their downstream ends to define said divergent annular passage and said combustion zone and including means to inject fuel and sustain combustion in said parallel walled annular passage to establish a pilot combustion zone therein to serve as a pilot flame for the primary combustion zone.
 59. Apparatus according to claim 53 and including selectively oriented flow guide means operatively associated with said helically directed slots in said first and second duct members of said dilution zone mixer, which guide vane and slot combination is selectively oriented to produce a tangential velocity Vt5 which is substantially larger than tangential velocity Vt6.
 60. An annular combustion chamber concentric about an axis providing compound mixing with radial and axial staging including a combustion zone axially spaced from a dilution zone and wherein said combustion zone includes: A. a concentric mixer comprising:
 61. Apparatus according to claim 60 wherein said helical slots in said first and second duct members of said dilution zone mixer are oppositely disposed.
 62. Apparatus according to claim 60 and including guide vanes operatively associated with said slots in said first and second duct members of said dilution zone mixer and shaped to cooperate with said slots so that tangential velocity Vt4 is larger than tangential velocity Vt5.
 63. Apparatus according to claim 60 wherein the first annular passage defines the primary combustion zone downstream of said combustion zone mixer splitter duct, and wherein said second fluid is combustible fuel-air mixture flowing through said third annular passageway into said primary combustion zone and wherein said first fluid is a combusting fluid operating as a pilot flame and flowing into said primary combustion zone to mix with and ignite said second fluid to combust therewith in said combustion zone to form said third fluid which is the products of combustion formed in said primary combustion zone, and further, wherein said first and second duct members of said dilution zone mixer form said dilution zone in saiD seventh annular passage and wherein said fourth and fifth fluids are diluent fluids which enter said dilution zone from said fifth and sixth annular passages to mix with and cool said primary combustion zone products of combustion in said dilution zone.
 64. Apparatus according to claim 60 and including trigger means attached to the downstream end of said splitter duct of said combustion zone mixer to stir the interface of the first and second fluids flowing thereover.
 65. An annular combustion chamber concentric about an axis and having a primary combustion zone positioned forward of a dilution zone and having a barberpole mixed immediately forward of the primary combustion zone and including: A. outer and inner wall members of circular cross-section and concentric about an axis and supported so as to diverge in a downstream direction to form a first annular passage of a divergent nature therebetween, B. a first duct member of circular cross-section positioned in said first annular passage coaxially with said wall members and cooperating with said inner wall member to define a second annular passage therebetween, C. a second duct member of circular cross-section positioned coaxially with said wall members and positioned between said first duct member and said outer wall member and cooperating with said outer wall member to define a third annular passage therebetween and with said first and second duct member shaped and positioned to define a fourth annular passage which diverges in a downstream direction therebetween, and at least partially envelopes the primary combustion zone and with said first and second duct members having an upstream end positioned downstream of the upstream end of said inner and outer wall members, D. means to inject fuel into said first annular passage at the upstream end thereof so as to provide a fuel-air mixture into said second, third and fourth annular passages. E. at least one row of helically directed circumferentially oriented slots extending through said second duct member to place said third annular passage into communication with said fourth annular passage, F. at least one row of helically directed and circumferentially oriented slots extending through said first duct member to place said second annular passage into communication with said fourth annular passage, G. a first cascade of selectively oriented flow turning vanes positioned at substantially the upstream end of said fourth annular passage and extending circumferentially therearound, H. flameholder means positioned immediately downstream of said cascade of vanes and positioned substantially at the mid-radial position thereof to establish a recirculation zone downstream thereof, I. a second cascade of selectively oriented vanes positioned circumferentially around and at substantially the upstream end of said second annular passage, J. ignitor means located in said fourth annular passage, the vanes of said first cascade being oriented so that the fuel-air mixture passing thereover from said first passage and ignited downstream thereof by said ignition means to combust downstream of said flameholder produces a combusting fluid of density Rho 1 and tangential velocity Vt1 in said fourth annular passage and said primary combustion zone, the slots of said second duct member being oriented so that the fuel-air mixture passing therethrough from said first annular passage will constitute a fuel-air mixture flowing into said primary combustion zone at density Rho 2 and tangential velocity Vt2 to be ignited by and burn with said first fluid in said primary combustion zone, the vanes of said second cascade and the slots in said first duct member being shaped and oriented to cooperate and cause the fuel-air mixture which passes through said second annular passage from said first annular passage to pass over said second vane cascade and through said slots of said first duct Member to enter the primary combustion zone as a fuel-air mixture of density Rho 3 and tangential velocity Vt3 so as to be ignited by and combust with said first fluid and the fuel-air mixture from the third annular passage in said primary combustion zone, and wherein said vanes and slots are selectively shaped and oriented that the following product parameter relationship exists: Rho 3 Vt32 > Rho 1 Vt12 > Rho 2 Vt22
 66. Apparatus according to claim 65 and including means to cool said outer and inner wall members.
 67. Apparatus according to claim 65 and including means to dilute and cool the products of combustion from said primary combustion zone in said dilution zone.
 68. An annular combustion chamber concentric about an axis and having a primary combustion zone and including: A. inner and outer duct members of circular cross-section and positioned coaxially about said axis and shaped to define an annular passage therebetween and communicating with the primary combustion zone at its downstream end, B. means to pass a swirling fuel-air mixture through said annular passage with both tangential and axial velocity about said axis, C. a combustion flameholder mechanism located in said annular passage between the inlet thereof and the primary combustion zone and comprising:
 69. An annular combustion chamber concentric about an axis and having a combustion zone located axially forward or upstream of a dilution zone and including: A. inner and outer duct members of circular cross-section and positioned coaxially about said axis and shaped to define a diverging annular passage therebetween increasing in cross-sectional area in a downstream direction and communicating with the primary combustion zone at its downstream end, B. means to pass a swirling fuel-air mixture of density Rho 1 through said diverging annular passage at tangential velocity Vt1, C. a combination flameholder and mixing trigger mechanism located in said annular passage between the inlet thereof and the primary combustion zone and attached to the outer duct member and comprising a convoluted ring with convolutions increasing in a downstream direction and extending around the periphery of said annular passage and with said convolutions being in substantially helical shape to substantially assume the direction of flow of the fuel-air mixture passing through the annular passage and including a plurality of apertures on the walls thereof to permit some of the fuel-air mixture from the annular passage to pass therethrough into the interior of said flameholder mechanism, D. ignitor means operatively associated with said flameholder and trigger mechanism to ignite the portion of the fuel-air mixture entering the interior of said flameholder mechanism through said apertures to form a combusting fluid of density Rho 2 and having a tangential velocity Vt2 imparted thereto by the convolutions of the flameholder to establish the product parameter relationship Rho 2 Vt2 is less than Rho 1 Vt12 so as to establish an unstable and convoluted interface between the fuel-air mixture of the annular passage and the products of combustion so as to accelerate mixing and combustion therebetween in said primary combustion zone.
 70. Apparatus according to claim 68 and including means to cool said outer and inner duct members.
 71. Apparatus according to claim 69 wherein said combination flameholder and trigger mechanism has helically directed convolutions which trough at their minimum radial station and peak at their maximum radial station and including: A. means to improve triggering performance of this combination flameholder and trigger mechanism comprising:
 72. Apparatus according to claim 28 wherein said duct is of circular cross-section and including means to cause said fluids to flow in coannular side-by-side relationship.
 73. Apparatus according to claim 28 wherein said combustion chamber is an annular combustion chamber and wherein said flow path of said two dissimilar fluids is coannular.
 74. Apparatus according to claim 28 wherein the flow paths of said two dissimilar fluids is about a common center of curvature. 